THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

[18:00:00]

BRIANNA KEILAR, CNN HOST: What he learned in a high-level briefing a short time ago.

U.S. response. The CIA chief is warning that what happened in Istanbul could happen here and that ISIS may be plotting similar attacks right now. We will tell you what airports in this country are doing and may do next to try to keep terrorists out.

Carnage to cleanup. The Istanbul Airport is open again just hours after dozens of people were killed by explosions and gunfire. What lessons can the U.S. and other countries learn from the rapid push to get back to normal?

And candidate candor. Donald Trump seizes on this new attack, vowing he would get vicious with terrorists and bring back water-boarding, his remarks in stark contrast with claims that Trump is trying to tone it down.

We want to welcome our viewers in the United States and around the world. Wolf Blitzer is off. I'm Brianna Keilar, and you're in THE SITUATION ROOM.

ANNOUNCER: This is CNN breaking news.

KEILAR: Breaking news tonight, growing indications that ISIS is behind the deadly attack at one of the world's busiest airports.

CIA Director John Brennan says the suicide bombing in Turkey bears the hallmarks of the terror group, although there's been no official claim of responsibility. Brennan is warning that ISIS may be planning similar attacks here in the United States.

And the death toll is now up to 41 after three bombers opened fire and then blew themselves up before reaching the security checkpoint. Another 239 people were injured. More than 100 of them are still in the hospital. The airport reopened, though, just hours after the attack, even as investigators hunt for more information about the bombers.

Turkish officials say the taxi driver who brought the killers to the airport has been questioned and released. And after the panic and bloodshed overseas, some major U.S. airports have ramped up security tonight. And CNN has learned that federal officials are considering widening the ring of security around airports in this country.

I will ask the chairman of the Senate Homeland Security Committee, Ron Johnson, what he learned in a high-level briefing just a short time ago. And our correspondents, analysts and guests have full coverage of this breaking story.

First, I want to get to CNN senior international correspondent Clarissa Ward.

Investigators, Clarissa, have been sharpening their focus on ISIS.

CLARISSA WARD, CNN SENIOR INTERNATIONAL CORRESPONDENT: Well, Brianna, it's traditionally has not claimed responsibility for attacks that they carry out in Turkey. Now, that may be because the group thrives on the uncertainty and instability that causes.

But one thing we do know. ISIS has repeatedly, in its propaganda, singled out Turkey as a major target. And Turkish officials tell CNN that they believe that the attackers were foreigners, again pointing finger at ISIS.

(BEGIN VIDEOTAPE)

WARD (voice-over): Tonight, investigators in Turkey and the U.S. want to know if the brutal airport attack was coordinated and directed from abroad or if the terrorists who killed 41 and wounded hundreds of others were acting alone.

Sources say, either way, the two-pronged assault had all of the hallmarks of an ISIS operation, three men wearing explosive vests carrying AK-47s exiting a taxi curbside, shooting at panicked travelers before blowing themselves up.

LAURENCE CAMERON, WITNESS: I just heard these screamed. I turned around the corner, and it's just this wall of people running towards me, tripping over themselves. Police with guns out. Just pure panic.

WARD: Much of the attack, the deadliest ever at an airport, was captured on video, passengers seen fleeing bullets and hiding in stores.

Security footage appears to have captured two of the blasts, this one outside an arrival terminal, the other moments later as an attacker runs through a departure hall. He's shot by police, then falls to the ground, dropping his weapon. Seconds later, he also detonates his suicide vest.

Despite the carnage, today, just hours after the massacre, an eerie calm and the veneer of a return to normal, the Turkish government quickly washing away the blood, repairing windows, and reopening one of the world's busiest airports to international flights.

Today, the ISIS-affiliated Aamaq news agency posted this message celebrating the two-year anniversary of the establishment of what it calls the caliphate or Islamic State, pointedly saying that ISIS has covert units in Turkey and elsewhere. And while no group has officially claimed credit, tonight, officials in the U.S. and Turkey say they have few doubts about the motive.

JOHN BRENNAN, CIA DIRECTOR: There's no credible claim of responsibility at this point. But that's not very surprising, because, at least in most instances, if not all, ISIS has not claimed credit or responsibility for attacks that are perpetrated inside of Turkey.

(END VIDEOTAPE)

WARD: ISIS has taken a lot of hits this year, losing precious oil revenue and territory, which has hurt their credibility.

Don't forget, their actual motto is (SPEAKING ISLAMIC) meaning remaining and expanding. So, if they are shrinking, Brianna, that hurts them. And that may be the reason we're seeing them lash out with these high-profile splashy attacks on soft targets.

[18:05:14]

KEILAR: All right, Clarissa, thank you so much for that report.

Tonight, President Obama says the United States will do what's necessary to protect Americans from terrorists.

CNN White House correspondent Michelle Kosinski is with the president in Canada at the Summit of North American Leaders.

What else did the president say about this attack, Michelle?

MICHELLE KOSINSKI, CNN WHITE HOUSE CORRESPONDENT: Hi, Brianna.

Well, President Obama and White House officials aren't definitively saying that this attack was the work of ISIS, but they're absolutely talking as if it was.

President Obama talked about his phone call this morning with Turkey's President Erdogan, offering any and all U.S. assistance that can be requested.

And, remember, it was only two weeks ago that Erdogan was calling President Obama and offering his condolences after the Orlando terror attack. And what we keep seeing is that virtually every time President Obama goes one of these foreign trips, where he would focus on other issues many times, it's interrupted by or overshadowed by global terror.

So, we're hearing from the White House today is concern that ISIS is still able to launch these kinds of attacks, as well as commitment among coalition countries, including Turkey, to defeat it.

Listen. (BEGIN VIDEO CLIP)

BARACK OBAMA, President of the United States: We're still learning all the facts.

But we know this is part of our broader, shared fight against terrorist networks. And we will continue to work closely with Turkey to root them out. And, meanwhile, we're going to do what's necessary to protect our people.

I'm confident that we can and we will defeat those who offer only death and destruction, and we will always remember even as there are those who are trying to divide us that we're stronger when we come together and work toward a better world together.

(END VIDEO CLIP)

KOSINSKI: As President Obama is here in Canada, we saw today Vice President Biden and Jill Biden signing a condolence book at the Turkish Embassy in Washington, D.C.

Also, the White House today emphasized how it's been prioritizing a continued question. How much is Turkey doing? Is it doing enough to secure its border with Syria, where thousands upon thousands of foreign fighters have been able to cross back and forth, which of course is a risk not just to Turkey, but to other countries, including the United States?

They emphasize the importance of that work, that there has been progress. There's still, though, about a 60-mile stretch that's unsecured, ISIS has control, and the White House acknowledged that more needs to be done on that -- Brianna.

KEILAR: All right, Michelle Kosinski traveling with the president.

We're actually -- we were looking at some live pictures there as we see that signing of the condolence book, the vice president there in Washington at the Turkish Embassy, a very somber event there, as he pays his respect, not long after Turkey paid their respects to the U.S. just a short couple weeks ago.

And now to the terror threat at airports here in the United States and concerns that the ring of security needs to be extended to prevent attacks like the ones that we just saw in Turkey.

And now, tonight, CNN has learned that security officials in the United States have been discussing for quite some time the idea of extending the security perimeter at airports beyond the TSA checkpoints as a way to better protect soft targets at airports. A U.S. official tells me the discussions were happening months before

this second major airport bombing.

(BEGIN VIDEOTAPE)

MARSH (voice-over): It's the second time in three months terrorists have struck the so-called soft target area of an airport, the space before the security checkpoint that's filled with passengers, but not nearly as secure.

JULIETTE KAYYEM, CNN NATIONAL SECURITY ANALYST: What has been shown in Brussels and in Istanbul is that, even if you fortify a soft target, there will be always be another soft target or soft area. And that's essentially what the terrorists are doing, is that they see a security apparatus built and then they just back off 10 feet and deploy in those areas that are more public.

MARSH: The threat to airport soft areas makes the long wait times seen across the country not only an inconvenience, but a security concern.

Following the Istanbul attacks, some U.S. airports have ramped up security at their perimeters. In New York and New Jersey, officers are equipped with tactical weapons. In Miami and Atlanta, there's an increased police presence.

In the U.S., the Department of Homeland Security is responsible for airport security checkpoints. CNN has learned the agency has discussed options to extend its security reach. The idea is widening the security presence, perhaps to the entrance or possibly the parking lot.

[18:10:10]

But former DHS follow Juliette Kayyem says that wouldn't be effective.

KAYYEM: Certainly, you could extend the security 10 miles away from an airport, and guess what? The vulnerability will be at mile 10.1. And so at some stage, we just have to accept a level of vulnerability, given the threat that we have today.

MARSH: Because Istanbul's airport has several direct flights to and from the United States, DHS requires strict screening procedures comparable to U.S. standards. The head of the TSA told CNN in May, if those rules are not followed, flights could be prohibited.

(on camera): How often do you go over to check up on these airports?

PETER NEFFENGER, TSA ADMINISTRATOR: If we have got a reason of concern, it can be as frequently as every week. And then if you have got a reason that you trust, it can be less frequent than that.

MARSH (voice-over): But regardless of the standard and police presence, it's impossible to eliminate all airport vulnerabilities.

(END VIDEOTAPE) MARSH: Well, currently, airport perimeter security is the responsibility of airports, local and sometimes state law enforcement.

Although DHS has been discussing ways to extend the security line at U.S. airports, the agency has not at this point identified the most effective way to do that. Extending that security line could mean missed flights. Passengers would have to be at the airport even earlier. Of course, that would take more manpower and money, Brianna.

KEILAR: And time. Rene Marsh, thank you so much.

A short while ago, U.S. senators received a high-level briefing on the ISIS threat as the investigation into the airport terror attack intensifies.

We're joined now by the chairman of the Senate Homeland Security Committee, Ron Johnson. He's also on the Senate Foreign Relations Committee.

Sir, thank you so much for being with us.

And I know that this was a briefing that you had with Defense Secretary Ash Carter, I believe, if that's right, the chairman of the Joint Chiefs, other top intelligence voices.

SEN. RON JOHNSON (R), WISCONSIN: That's right.

KEILAR: What can you tell us? What can you share from that?

JOHNSON: Well, I can share that you're reporting on this incident in Istanbul is pretty accurate.

You're getting the facts correct. And we do not know yet who the perpetrator is. Nobody's claimed credit for it. It has all the hallmarks of ISIS. And so that's what we know. We also know that as long as ISIS continues to exist, these threats are going to continue and we're going to see more and more of these tragedies.

And it's depressing how frequently they are occurring.

KEILAR: Especially with John Brennan saying today that he would be very surprised if ISIS isn't planning something similar in the U.S.

But I would refer to you to CIA Director Brennan's testimony a couple of weeks ago in front of the Senate Intelligence Committee where he said that our efforts have not reduced ISIS' terrorism capability and global reach, and they remain a formidable, resilient and largely cohesive force.

Now, that's really pretty depressing after 22 months of effort. This is 22 months after President Obama laid out America's goal as it relates to ISIS, which was to degrade and defeat them. We haven't defeated them. We're nibbling around the edges. We made some progress.

But I continue to use the analogy of a beehive. You have got a beehive out in your backyard, you go out and poke it with a stick and do some damage to it, but in many respects, you make it more dangerous. The better thing is to take out the hive. We need to take out ISIS, or else we're going to continue to lose more and more of our freedoms.

Look what we're talking about right now. Extending the security zones, that is just going to create another pinch point, reduce our freedoms further. We have got to get serious about actually accomplishing President Obama's goal, which is defeating ISIS.

KEILAR: How concerned are you, especially as we go into this travel weekend, about security at U.S. airports?

JOHNSON: Oh, we always remain concerned.

So, it's extremely important for every American citizen to have a heightened sense of alert status. If you see something, you have to say something. I think what we have always seen in the past is people, because of political correctness, are a little concerned about saying something.

We can't be. These threats are real. They're growing. And it's the world we live in today. And I'm getting sick of it. Personally, I'm getting sick of it. I actually remember many years ago being able to go through an airport, hop on a plane without having a body search or going through an advanced imaging technology machine or metal detector.

We are getting -- we're getting numb to the effect of Islamic terror in our lives. And we all need to get sick of it and we need to demand that we actually defeat it.

KEILAR: The difference is very clear as you go through those checkpoints. I can attest to that as well.

Expanding the security perimeter, the Ataturk Airport, that what they had there. In the U.S., generally speaking, you get out at the curb, out of the cab, or out of the car you came in, and you walk through doors, you check in, then you go to your security checkpoint.

[18:15:01]

As soon as you would get out of the curb, there would be an initial checkpoint before even checking in. Is that something you're behind?

JOHNSON: There's going to be another pinch point, another gathering of citizens.

(CROSSTALK)

KEILAR: You don't see what's gained. You don't see what's gained there.

JOHNSON: I think the better approach -- and I know DHS is beefing up training for the airport authorities and local police officers that have that security responsibility.

I'm a big proponent of increasing the number of canine units. If you're concerned about potentially bomb threats, drugs or other threats, there's no technology that beats the nose of a dog.

So, I would dramatically increase that. We have probably got actually operational less than 1,000 canine units tasked for this particular task. We should double, triple or quadruple that. I think that would be -- that actually would improve our security. Now, it costs money, but let's not be penny-wise and pound-foolish on this.

KEILAR: Was there any talk today? You were in this briefing.

When I think of the arrivals area, which is where it appears these attackers came through, and you think of, generally speaking, a lone TSA agent monitoring that area, where it's the final -- it's where you leave if you're coming -- if you're arriving into the airport and then you go beyond a certain point, you can't turn back.

There seems to be some vulnerability there. Is there any concern and any plan to address that?

JOHNSON: I know Admiral Neffenger is really doing a top-to-bottom review. He's been on the job about a year.

I think they are looking at a different layered approach across the board in terms of what we need to do in terms of airport security, because that remains a target of Islamic terrorists, is really attack that vulnerability in terms of air traffic and air travel.

So, we need to keep looking at that. But, again, I will go back to the point. So much of these secure briefings are hearings with other administration officials. They're claiming some progress against ISIS. And it's true.

We are making progress, but not fast enough. And as long as ISIS exists, as long as we hold that territory, they will be able to claim that caliphate. They're going to be perceived as winners. They're going to continue to inspire the type of activity we saw in Orlando and San Bernardino, and now again in Turkey.

This is depressing, how frequent these things are becoming. We have got to take that threat seriously and we have got to defeat ISIS.

KEILAR: I have many more questions for you. Senator Ron Johnson, stay with me. We will have more after a break.

(COMMERCIAL BREAK)

[18:21:28]

KEILAR: We're back with the Senate Homeland Security chairman, Ron Johnson, as officials in the United States and Turkey grow more convinced that ISIS is likely behind this terror attack at the Istanbul Airport.

I'm going to have you stand, Senator. We have more questions for you.

But, right now, by our global affairs correspondent, Elise Labott, has more on this attack and also the bigger picture, the global war against ISIS.

And U.S. and Turkish officials fear it will not be the last. They are hundreds of Turkish nationals fighting for ISIS that are going to be coming home from the battlefield in Syria. And tonight there are new reports that the Turkish police are warning that ISIS could have sleeper cells throughout the country.

And after months of warning about the growing threat posed by ISIS, tonight, officials are hoping that Turkey will be more committed to the fight against the terror group, a fight that has not until now been its greatest priority.

(BEGIN VIDEOTAPE)

LABOTT (voice-over): Turkey is reeling from a night of terror that shook Istanbul's main international airport. Security cameras captured dramatic scenes of terrified travelers scrambling to safety moments before one of the blasts.

OSMAN UCAR, WITNESS (through translator): Police told us to lie down. They were shooting at the police and the police were shooting at them. Someone next to us got shot. And then we saw the bomb near the X-ray explode. Everyone around it died in the blast.

LABOTT: Still no claim of responsibility, but that didn't stop the Turkish government or the U.S. from pointing the finger at ISIS.

CIA Director John Brennan said he's not surprised by the group's silence.

JOHN BRENNAN, CIA DIRECTOR: They carry out these attacks to gain the benefits from it in terms of sending a signal to our Turkish partners, but at the same time not wanting to potentially maybe alienate some of those individuals inside of Turkey that they may still be trying to gain the support of.

LABOTT: In the wake of the attacks, Turkish President Erdogan is calling for a united global front against terrorism.

And today President Obama called his NATO ally to make that pledge.

BARACK OBAMA, PRESIDENT OF THE UNITED STATES: To reaffirm our strong commitment to partner with Turkey, with NATO, with the broad-based alliance that we have structured around the world to fight ISIL.

LABOTT: ISIS is blamed for several deadly attacks against Turkey, the worst last October, when 95 civilians were killed at a peace rally in Ankara. Turkey, a critical member in the coalition against ISIS, the one the U.S. says has been foot-dragging, accusing President Erdogan of turning a blind eye to foreign fighters and weapons flowing into Syria from Turkey, even quietly supporting jihadi groups and focusing more on ousting President Assad in Syria and squeezing Kurdish separatists like the PKK, who have also launched deadly attacks against Turkey.

JAMES JEFFREY, FORMER U.S. AMBASSADOR TO IRAQ: Turkey at one level is fighting ISIS, but it sees the PKK Kurdish terrorists and the Assad regime as even bigger threats.

LABOTT: Turkey has allowed the U.S. to use its key Incirlik Air Base to conduct airstrikes and is now firing artillery at ISIS from across the border.

It's cracking down on the flow of foreign fighters as it tries to support a flow of refugees. But with ISIS networks already taking route throughout the country, it could be too little, too late.

(END VIDEOTAPE)

[18:25:02]

LABOTT: Now, the Istanbul attacks do coincide with a recent agreement by Turkey to allow NATO to step up patrols against ISIS along its border with Syria, as well as steps taken by President Erdogan just this week to normalize ties with Russia and Israel.

Now, these all could be possible motives for the attack on the airport, but could also give Turkey important allies as it steps up its campaign to combat the growing ISIS threat, Brianna.

KEILAR: Elise Labott at the State Department, thank you.

And we're back again now with the Senate Homeland Security Committee chairman, Senator Ron Johnson.

Thanks for coming back to talk with us.

And I do want to know just the biggest picture here of what your biggest concern is at this point. Is it a lone wolf, ISIS-inspired attack for the U.S., or would it be more an ISIS- directed or al Qaeda-directed attack?

JOHNSON: Well, both are possible.

I think right now the history has been in America, it has been that lone wolf-inspired terrorist. And, of course, ISIS, there's no doubt about it, we have made progress. It's more difficult to get into Iraq and Syria. And so ISIS is responding, they're evolving. They're metastasizing. They're saying don't come here. It's difficult to come join the fight here in Iraq and Syria. So, kill in place. Kill where you are. And so people are taking them up on their directive. And that's extremely difficult for public safety officials to track those people.

We're seeing it time and time again. What do you do with the not guilty yet? We can do postmortems on these things. We can Monday morning quarterback. But it's enormously difficult in a free society where people have constitutional rights. We have freedom of speech. How do you deal with that?

So, from my standpoint, you discuss all these things and people distract with different non-solutions. We have to defeat ISIS. We have to go right back to where this is all occurring and recognize the mistakes we have made, not leaving a stabilizing force behind in Iraq. That's a strategic blunder of historic proportions.

ISIS was allowed to rise from the ashes of what was a clearly defeated al Qaeda in Iraq. Now we're dealing with the consequences. And as we were discussing earlier, President Obama is not allowing his military personnel to utilize the resources that they could bring to bear to make sure that ISIS is defeated a whole lot sooner than what they may be defeated.

We had testimony from Brett McGurk, said that back in September 2014, when President Obama laid out that goal of defeating ISIS, there was a three-year plan to do so. Well, we're 22 months into that plan, and we haven't even pushed them out of Iraq. And they're going to be much more difficult to push out of Syria, because we don't have a governing authority that's really cohesive that is supporting us in Syria, like we do in Iraq.

KEILAR: Senator Ron Johnson, thank you so much for coming basically from this briefing that you got and just discussing your concerns with us and the lay of the land. Thank you so much.

JOHNSON: Happy to do it.

KEILAR: Just ahead, we will go live to Istanbul for the latest on the terror investigation and how this airport reopened so quickly after the attack.

Plus, Donald Trump on the campaign trail tonight talking about terror and addressing concerns that his get-tough approach may be too tough.

(BEGIN VIDEO CLIP)

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: They say, oh, can we trust Donald with the button? Well, I'm the one that didn't want to go into Iraq, just so we understand it. I would be the slowest with the button, but I would be the one that doesn't have to use it because they are going to respect us again. Nobody respects us now.

(CHEERING AND APPLAUSE)

(END VIDEO CLIP) (COMMERCIAL BREAK)

KEILAR: We're back now with breaking news.

[18:33:07] A fresh warning from the CIA director that ISIS may be planning a casualty terror attack inside of the United States similar to the carnage that we just saw in Turkey.

Let's bring in our CNN senior international correspondent, Nima Elbagir. She is at the Ataturk Airport in Istanbul. What's the latest there on the ground, Nima?

NIMA ELBAGIR, CNN SENIOR INTERNATIONAL CORRESPONDENT: Well, what's firming up for officials here is a sense of how all of this unfolded, and what's emerging, really, is a picture of a pretty meticulously planned attack.

You have the three gunmen opening up fire at the outer security perimeter but within the airport compounds. And it was while they were exchanging a sustained exchange of gunfire with authorities and the first detonation, that enabled two of them to escape, to move in under cover of confusion, in past the X-ray machines, past that first hard security perimeter here on the ground floor in the arrivals halls just behind me.

And while that second attacker detonated and was being held off by authorities, the third attacker managed to get outside and be there when that wave of fleeing passengers came out.

This is incredibly concerning for authorities but not just here, in the U.S. and across Europe. Because there are very few airports anywhere, barring perhaps somewhere like Baghdad or Kabul that have an entirely secured airport compound. And this is clearly something that these attackers are now taking into account in their planning.

And doubly, if not equally as concerning for authorities here is the indications they're finding that these attackers were foreign. So you have a meticulously planned attack.

One official called -- described it to me as sophisticated. Then you have the potential of a broader foreign network that was able to infiltrate the -- able to infiltrate inside Turkey. And now what they're thinking, Brianna, is who else is out there, and the clock, of course, is ticking -- Brianna.

[18:35:10] KEILAR: Nima Elbagir for us in Istanbul, thank you.

And let's bring back CNN senior international correspondent Clarissa Ward, along with CNN senior law enforcement analyst Tom Fuentes, CNN national security analyst Peter Bergen. And we also have CNN counterterrorism analyst Philip Mudd.

Phil, the CIA director said something pretty alarming today. He said he'd be surprised if ISIS wasn't trying to launch this same type of attack here in the U.S. You worked at the CIA. So what are the steps that U.S. authorities need to be taking right now? PHILIP MUDD, CNN COUNTERTERRORISM ANALYST: Brianna, this isn't just

about ISIS. You've got two enemies here. Enemy one is ISIS. Enemy two is time.

There's a couple questions you've got to ask here, and you need answers immediately. Question one, who are the folks that just did this, the terrorists who just did this in Turkey? I need names. I need identifying information like phone numbers and e-mail to determine whether they've got a broader network we need to disrupt.

No. 2, I've got to trace their training, their indoctrination back to Syria so organizations like the CIA and John Brennan can say, if there are individuals at the heart of ISIS who are sending operatives out to Turkey, can we take them out before they send operatives to New York and Washington?

And finally, if you're talking to the FBI director in the United States, you've got one question: Do we have cases in this country we're sitting on, where we're trying to collect more intelligence and we decide overnight we don't have that kind of time anymore? We've got to wrap them up, Brianna.

KEILAR: Tom, how much information is being shared, do you think, between Turkey and the U.S.? And is Turkey equipped to deal with those things that Phil just laid out?

TOM FUENTES, CNN SENIOR LAW ENFORCEMENT ANALYST: Well, the FBI over the years has had a pretty good relationship in Turkey with the officers in Ankara, as well as the officers in Istanbul, working with the police and their intelligence service. So I'm sure they're sharing what they have, but what do they have? That's the point.

At this point, they're unable to identify these people. If they don't have DNA to match them to, they're probably not going to have fingerprints or facial recognition or anything else, with the condition of the bodies of the terrorists. So, you know, they're in a difficult spot. They can say, well, probably foreigners because the taxi driver may have said they were speaking a different language, but other than that, identifying these three people is going to be a tall order.

KEILAR: Do you think, Peter, that eventually they will be able to or it's just too challenging?

PETER BERGEN, CNN COUNTERTERRORISM ANALYST: Well, I mean, I defer to Tom. I mean, it sounds like, from a forensic point of view, this is very, very difficult to do.

KEILAR: Yes. And, you know, I guess the bigger picture here, you look at -- and we've been talking about this -- look at the TSA checkpoint. That's sort of the last -- I mean, that is the last line of defense. Right? Not a TSA checkpoint there but a security checkpoint. The bigger picture is where is ISIS, you know, taking its fight? And obviously, there's a border between Turkey and Syria. Has Turkey done enough to stem the flow of resources and fighters, and how do you think this is going to change? BERGEN: Well, just think of the U.S.-Mexico and how porous that is.

So I mean, borders this long are difficult to secure. But that said, you know, Turkey has came in for a lot of criticism. They've -- you know, ISIS has begun to say in its own propaganda that "We're concerned about what the Turks are doing. Don't trust the Turks." And so this is one of the motivations if, indeed, ISIS was behind this attack. This is one of the two big motivations that ISIS would have to attack, because Turkey went from a sort of laissez-faire attitude towards these foreign fighters coming in, and now they've really cracked down in the last year or so.

KEILAR: You've seen this: Is it a new tactic? Would we say that? I mean, when you're talking about these suicide fighters using multiple types of weapons, multiple attackers, coordinated attacks, how has this evolved?

WARD: It's not really a new phenomenon. I mean, actually, it has precedents as far back as, like, the time of the Prophet Mohammed. This idea of the inghamasi or whatever comes from the root Arabic word "to plunge deeply," to plunge deeply into the enemy. The idea being that you weren't going to come back alive.

So the purpose of these kind of special forces, essentially, is what they are, is that they're highly trained to do as much damage as they can as possible with their guns before detonating their vests at the last moment, ideally in an attempt either to evade capture or to kill security or law enforcement, who may be getting closer to them or circling in on them. We have seen militant jihadist groups use these tactics before.

But what I would say is that, for ISIS, it has now become their sort of go to model almost. We saw something very similar in the Bataclan theater in Paris. They go in with those heavy weapons. They kill as many people as they want. And when the police arrive on the scene, that's when they blow themselves up.

FUENTES: Plus, we haven't even talked about the fact they might have between 5 and 10,000 employees at that airport. What about the insider threat? We're talking about guys that came through the doors with guns blazing and the bombs detonating. But there could be a lot of radicalized employees already in that airport, prepared to do something different next time.

KEILAR: We're in the last several days of Ramadan, Peter. What are you expecting ahead or can you tell?

[18:40:05] BERGEN: Well, we've -- yes, we've has a suicide -- in the last 48 hours, an ISIS suicide attack in Lebanon, one in Jordan. A series of ISIS suicide attacks in Yemen, probably in Turkey now at the airport. We've had ISIS-inspired attacks at Orlando and in Paris in the last two and a half weeks. It would be absurdly optimistic to conclude that there wouldn't be other attacks, either directed or inspired, over the next several days. That's a strong possibility.

KEILAR: And what is your biggest concern overall now? Is it -- when you're talking about the U.S., let's bring this back to the United States, because I think ahead of this travel weekend a lot of people are concerned. Is it still that lone wolf attack, that inspired attack carried out, even potentially by an American. We saw this in Orlando or San Bernardino. Could it get to the point where it's a much more structured ISIS-directed attack?

BERGEN: Every lethal terrorist attack in the United States since 9/11 has been carried out by an American citizen or American legal permanent resident with no formal connections to a foreign terrorist organization. That's really the threat. Of course, you know, something the change. But if we're going to see another attack it's most likely by a lone wolf or a pair of lone wolves.

KEILAR: And with lone wolves, are they, looking at what's happening, even with what appears to be -- we heard, certainly, from Senator Rubio earlier that he said this pointed to an ISIS-directed attack. With lone wolves, they're looking at what happened as a template. Right? For what they would want to do.

FUENTES: They also have television. They also have Internet. They also have the ability. So they're watching CNN, BBC, Al Jazeera, Sky News. They're watching the whole network of worldwide television every time there's one of these attacks, and they learn something from each of those that they might implement in a future attack.

So that's just the way it is. We either cover it or we don't. And when we do cover it, they learn something.

And coming up -- we're going to be back with more of our breaking news on the attack in Istanbul in just a moment.

(COMMERCIAL BREAK)

[18:46:39] KEILAR: Tonight, the CIA director said he's worried that ISIS is plotting similar attacks in United States as the terror group loses more ground on the battlefield. Despite recent gains ISIS, there are some critical problems with the coalition's air campaign.

Let's bring in our Pentagon correspondent, Barbara Starr.

Tell us about this, Barbara.

BARBARA STARR, CNN PENTAGON CORRESPONDENT: Well, hi, Brianna.

You know, the CIA is saying there's still a long way to go to make significant progress against ISIS. This, just as one of the most senior officers are telling me that targeting is not what it should be.

(BEGIN VIDEOTAPE)

STARR (voice-over): In exclusive interview, the chief of Air Force intelligence tells CNN air strike targeting against ISIS getting a failing grade. On scale of 1 to 10, how far behind is targeting? LT. GEN. ROBERT OTTO, U.S. AIR FORCE: I would give us a five, which

means we have a lot of work to do.

STARR: The problem?

OTTO: The problem is not having enough fighter jets to drop bombs. The problem is having enough legitimate targets that we can strike that can put ISIL on their heels.

STARR: The Pentagon has been trying to find better ways to select ISIS targets that if bombed could hurt the organization. The general describes a disjointed process.

OTTO: We are tracking targets off of probably a couple dozen spreadsheets and it's not coordinated between all the agencies.

STARR: A startling assessment after 13,000 air strikes.

OTTO: There's always room to improve.

STARR: The airstrikes are helping to take back territory. On this section of the Syria-Turkey border, the U.S. is focusing on shutting down the flow of fighters back and forth, conducting air strikes around this key area of Manbij in northern Syria.

BRETT MGGURK, U.S. ENVOY TO THE COALITION AGAINST ISIS: The sophisticated attacks like Paris and Brussels planned in Raqqah. They go up through this Manbij pocket area. They coordinate and organize in Manbij city, and then move out through Turkey to conduct their attacks.

STARR: And air strikes can disrupt ISIS finances. One example, half of ISIS' $300 million a year in oil earnings has been wiped out by air strikes, but still leaving them $150 million a year.

UNIDENTIFIED MALE: That's a lot of money. You can fund a lot of things across the globe.

STARR: Including the attack in Istanbul. ISIS is building a network of dozens of terrorists it can still send into Europe, officials tell CNN.

JOHN BRENNAN, CIA DIRECTOR: ISIL is training and attempting to deploy operatives for further attacks. ISIL has a large cadre of western fighters who can potentially serve as operatives for attacks in the West.

(END VIDEOTAPE)

STARR: So, five out of ten on air strike targeting. Look, General Otto is the head of air force intelligence. He's somebody worth paying a lot of attention to. He overseas programs involving about 30,000 intelligence personnel. He knows not everybody agrees with him but he also tells us, there are a lot of people inside the Pentagon that do -- Brianna.

KEILAR: Barbara Starr at the Pentagon -- thank you so much.

Just ahead, we're following the latest information coming in on the Istanbul terror investigation and the growing security concerns in the U.S.

And Donald Trump is talking tough on terror, saying the U.S. must fight fire with fire.

[18:50:02] But is he playing the politics of fear?

(COMMERCIAL BREAK)

KEILAR: Breaking news: the death toll from the Istanbul airport terror attack has risen to 42. More than 230 people have been injured, many of them critically and we'll stay on top of all these latest developments as they come in and bring them to you.

Meanwhile, President Obama has taken a new swipe at Donald Trump, rejecting the idea that the presumptive Republican nominee is a populist. Listen to the president in his self-described rant during a news conference in Canada.

(BEGIN VIDEO CLIP)

BARACK OBAMA, PRESIDENT OF THE UNITED STATES: They don't suddenly become a populist because they say something controversial in order to win votes.

[18:55:10] It's not the measure of populism. That's nativism or xenophobia or worse. Or it's just cynicism.

(END VIDEO CLIP)

KEILAR: On the campaign trail, Trump is ramping up his criticism of the president's handling of the war on terror and promising to get vicious with ISIS if he wins the White House.

CNN senior White House correspondent Jim Acosta is in Maine where Trump spoke just a short time ago.

Donald Trump continued to escalate his rhetoric on national security, pushing for a stepped-up battle against ISIS in the aftermath of the terror attack in Turkey and Trump's stark contrast and tone with Hillary Clinton is a preview for voters this fall.

(BEGIN VIDEOTAPE)

ACOSTA (voice-over): Donald Trump's battle cry for fighting terrorists after the airport attack in Turkey, an eye for an eye.

DONALD TRUMP (R), PRESUMPTIVE PRESIDENTIAL NOMINEE: You know, you have to fight fire with fire.

ACOSTA: Hours after the bombings, Trump called for a return to waterboarding terror suspects for information, a controversial interrogation tactic widely considered torture and banned by the Obama administration.

TRUMP: They probably think we're weak. We're stupid. We don't know what we're doing. We have no leadership.

ACOSTA: And the presumptive GOP nominee suggested without providing any evidence to back his claim that international and U.S. laws banning torture during times of war are standing in the way, emboldening groups like ISIS.

TRUMP: Their laws say you can do anything you want and the more vicious you are the better. So, we can't do waterboarding, which is -- it's not the nicest thing, but it's peanuts compared to many alternatives, right?

ACOSTA: Trump's heated response to the carnage in Istanbul was a departure from his toned-down scripted speeches on display in recent weeks. And it goes way beyond Hillary Clinton's more muted reaction to the attack in this tweet saying, "All Americans stand united with the people of Turkey against this campaign of hatred and violence."

Some Republicans like former POW John McCain aren't ready to adopt the Trump doctrine arguing waterboarding is torture.

SEN. JOHN MCCAIN (R), ARIZONA: If we torture people what do we expect our enemy would do to Americans that were captured? Does that open the door to that? I could go on for a long period of time. But in summary, it's not the United States of America.

ACOSTA: Trump is also on a tear on trade, promising voters he will rip up current U.S. trade deals like NAFTA and the proposed Trans Pacific trade deal.

TRUMP: The Trans Pacific Partnership is another disaster done and pushed by special interests who want to rape our country, just a continuing rape of our country.

ACOSTA: Trump's trade proposals prompted a rare rebuke from the normally GOP-friendly Chamber of Commerce, which tweeted, "Under Trump's trade plans, we would see higher prices, fewer jobs and a weaker economy."

All of that has top Republicans still reluctant to throw their full weight behind Trump.

SEN. MITCH MCCONNELL (R-KY), MAJORITY LEADER: So my hope is that he's beginning to pivot and become what I would call a more serious and credible candidate for the highest office in the land.

REPORTER: At the moment, I hear you saying he does not meet the threshold --

MCCONNELL: He's getting closer. Getting closer.

(END VIDEOTAPE)

ACOSTA: Now, near the end of his remarks in Maine, Trump falsely claimed that U.S. has not won any kind of military conflicts since the Vietnam War. Trump's return to this incendiary rhetoric can also be found in his latest fundraising appeal, Brianna. A Trump campaign email that went out earlier today calls on supporters to make a donation so they can, quote, "indict Hillary Clinton and find her guilty" -- Brianna.

KEILAR: And, Jim, there during this event, actually before the event and before Donald Trump even spoke, things got nasty. What happened?

ACOSTA: That's right. There was a warm up speaker for Donald Trump, talk radio host here in New England named Howie Carr. He was talking about Senator Elizabeth Warren who has gotten under Donald Trump's skin out on the campaign trail, going after the presumptive GOP nominee.

When Howie Carr was talking about Senator Warren before this crowd here in Bangor, Maine, there were people in the crowd shouting "Pocahontas" and Howie Carr before this audience of several thousand people here basically did a stereotypical native American battle cry, and the crowd ate it up. There were loud cheers for that.

It just goes to show that some of Donald Trump's very controversial rhetoric has big influence on his supporters -- Brianna.

KEILAR: All right. Jim Acosta for us in Maine -- thank you so much.

And please be sure to join us tomorrow in THE SITUATION ROOM. I will be back in for Wolf Blitzer.